The usual technique for forming fused biconical taper fibre optic couplers entails disposing respective segments of two or more optical fibres in intimate side-by-side relationship and heating the segments to a temperature sufficient to cause the fibre segments to soften and fuse together. The heated fibres are then longitudinally drawn to cause each of the fused fibres to develop a biconical taper and to thereby form the coupler. A typical disclosure of these steps is to be found in Abebe U.S. Pat. No. 4,612,028.